Convert one or two dates (date from and date to) into a sensible, legible date string

date_comparison.php

/**
 * Convert one or two dates (date from and date to) into a sensible, legible date string
 * @param  array $dates Array containing 'date_from' and (optionally) 'date_to'
 * @return string        Human-readable date text
 */
public function courseEntryDate(array $dates)
{

  $dates['date_from'] = $dates['day'];
  $dates['date_to'] = $dates['day_to'];

  $date_from = $dates['date_from'];

  if (empty($date_from)) {
    return '';
  }

  $date_to = $dates['date_to'] ?? '';

  $ts_date_from = strtotime($date_from);

  if (empty($date_to)) {
    return sprintf(
      __('am %s', 'sha'),
      date_i18n('d. F Y', $ts_date_from)
    );
  }

  $ts_date_to = strtotime($date_to);

  if (date_i18n('Ymd', $ts_date_from) == date_i18n('Ymd', $ts_date_to)) {
    // Same day
    return sprintf(
      __('am %s', 'sha'),
      date_i18n('d. F Y', strtotime($date_from))
    );
  }

  if (date_i18n('Ym', $ts_date_from) == date_i18n('Ym', $ts_date_to)) {
    // Same month
    return sprintf(
      __('vom %1$s bis %2$s', 'sha'),
      date_i18n('d.', strtotime($date_from)),
      date_i18n('d. F Y', strtotime($date_to))
    );
  }

  if (date_i18n('Y', $ts_date_from) == date_i18n('Y', $ts_date_to)) {
    // Same year
    return sprintf(
      __('vom %1$s bis %2$s', 'sha'),
      date_i18n('d. F', strtotime($date_from)),
      date_i18n('d. F Y', strtotime($date_to))
    );
  }

  return sprintf(
    __('vom %1$s bis %2$s', 'sha'),
    date_i18n('d. F Y', strtotime($date_from)),
    date_i18n('d. F Y', strtotime($date_to))
  );
}